Quote:
.... In practice there does not seem to be less wear in dirty engines with thicker oils.
aehaas
In diesel engines, as soot increases, wear increases. With thicker oils, that wear is less. You will see this especially in longer OCI's. The diesel engine UOA section and the tdiclub UOA collection is a good study and you will see the less wear with thicker oils, especially as OCI exceeds 10k.
The effect might be there with gasoline engines but many don't push their oil far enough to see it which is a good thing. Extended OCI crowd might see more wear with dirty thin oil vs dirty thick oil.
IMO, thicker oils protect better. But, my 3k OCI doesn't require it. My average
I do agree that 20wt doesn't provide any margin of safety if your fuel dilution spikes(short trippers, known pig rich vehicles, older leaky fuel injectors, tired sensors(map maf o2), excessive oil temps(turbo or known sludger), defective thermostat........if your vehicle has no oil temp control caused by marginal cooling, marginal sump capacity, low oil levels from consumption or negligence.....if your vehicle has marginal oil pressure or flow caused by oil varnish, sludge, questionable oil pump bypass spring, worn out tired oil pump, inadequate OEM oil flow or pressure.....if your vehicle has questionable cooling caused by small or clogged radiators, bad mech fan clutch or tired/undersized e-fan, weak/broken water pump, low coolant, improper ratios,....
Certain year Ford truck/suv 4.0, Lincoln 3.9, Villager 3.3, Zetec 2.0, any engine before 1993,... still use 5w30. Older FFV's get 10w30, while the rest get the 20wt. So, there is an issue with some applications that don't get lighter oils. I would think that temperature, PSI, flow, capacity, are the reasons why the 5w30 and 10w30's are being used.
Since I'm on an MPG hunt, I'm will be using thinner fluids once my mods are complete. I need to wire in fuel computer to bring back lean burn combustion(eliminate fuel dilution), remove the balance shafts(+10psi oil pressure and instant sump increase), improve filtration(bypass filter using surplus oil flow not feeding the balance shafts), improve oil temp control by using OEM wateroil heat exchanger,....until then my engine isn't going to see the 20wt.
AE, I understand that you have exotics. But the typical consumer vehicle isn't overengineered with surplus oil flow, pressure, cooling, sump capacity......that those exotic engines have. For example, I once drove a 3.3L Nissan Xterra(2+ ton vehicle) with a 3.5 quart oil sump, thimble filter, no oil cooling, engine worked 110% just to maintain barely reasonable performance, which ultimately caused oil consumption...... No way would I consider a 20wt in that vehicle. Synth oil provided some peace of mind knowing that oil wouldn't bake if a pint low. I also would think that the 40wt I used provided some additional film thickness, oil pressure, consumption control, and temp insurance. With a manual tranny, and aggressive driving, the crank and its thrust bearings, needed all the help they could get. The piston/ring/rod side loads are probably greater since the 3.3 is a stroker vg30e. I would think that a thin oil would've kill 'er quickly.
I find that too many 'common folk' vehicles are also underengineered. I won't blindly recommend moving to a thin oil. I do believe that there are many concerns for those that want to use thinner oils. Some of these concerns can be monitored with aftermarket oil filtration, aftermarket oil cooling, aftermarket accurate oil temp and oil pressure gauges, aftermarket higher volume and/or higher pressure oil pumps, improved water cooling via better waterpump and/or larger radiator, improve vehicle tuning via fuel computer of some sort(chip, EIFE, PMS),..........
